Field of the Invention
The present invention generally relates to respiratory methods or devices and methods and devices for providing heated and humidified gases to a user. More particularly, the present invention relates to techniques for measuring flow characteristics within such devices and tubes for use in medical circuits suitable for providing gases to and/or removing gases from a patient, such as in positive airway pressure (PAP), respirator, anaesthesia, ventilator, and insufflation systems.
Description of the Related Art
Many gas humidification systems deliver heated and humidified gases for various medical procedures, including respiratory treatment, laparoscopy and the like. These systems can be configured to control temperature, humidity and flow rates.
To provide a desired level of control, sensors must be used to detect flow characteristics. These sensors often are inserted directly into the flow and, because the sensors are not isolated from the fluid exchanges with the patient, the sensors must be cleaned or discarded. In other words, the sensors cannot be reused immediately after disconnection from the first patient. Such systems are described, for example, in U.S. Pat. No. 6,584,972, which is hereby incorporated by reference in its entirety.
Gas humidification systems also include medical circuits including various components to transport the heated and/or humidified gases to and from patients. For example, in some breathing circuits such as PAP or assisted breathing circuits, gases inhaled by a patient are delivered from a heater-humidifier through an inspiratory tube. As another example, tubes can deliver humidified gas (commonly CO2) into the abdominal cavity in insufflation circuits. This can help prevent “drying out” of the patient's internal organs, and can decrease the amount of time needed for recovery from surgery. Unheated tubing allows significant heat loss to ambient cooling. This cooling may result in unwanted condensation or “rainout” along the length of the tubing transporting warm, humidified air. A need remains for tubing that insulates against heat loss and, for example, allows for improved temperature and/or humidity control in medical circuits. Accordingly, it is an object of certain features, aspects and advantages of the invention to overcome or ameliorate one or more of the disadvantages of the prior art or to at least provide the public with a useful choice.